$\left[\begin{array} {ccc} 4\\ 7\\ 6\\ -1 \end{array}\right]$ What are the dimensions of the matrix?
Explanation: The first dimension is the number of rows in the matrix. There are $4$ rows. The second dimension is the number of columns in the matrix. There is $1$ column. In conclusion, the dimensions of the matrix are $4\times 1$.